Electrotinning wire

ABSTRACT

A high speed, high current density electrolytic apparatus for tinning wire provides a plurality of loops of wire simultaneously in opposite directions through the electrolyte. Alternate loops in a common plane are drawn in opposite directions to eliminate fluid drag problems. The wires pass through a tank having a bank of anodes and are guided by grooved rollers which separate the adjacent wires. Rotatable conductive drums on each side of the tank drive the wire in successive loops through the tank until a desired coating is obtained.

plane are awn in opposite directions to eliminate fluid drag problems. The wires pass through a tank having a bank-of anodes'and are guided by grooved rollers ytic apparar tinning wire provides a plurality of loops of wire simultaneously in opposite directions through the electrolyte. Alternate loops in a common dr Inventor: James Delves-Broughton, Mathern, England Assignee: International Standard Electric Corporation, New York, NY.

Filed: July 23, 1973 Appl. No.: 331,954

us. 204/206 204/28, 204/54 R Int. Cl. C23b 5/68, C23b 5/58, C23b 5/14 Field of Search........r........'.... 204/206, 207

References Cited UNITED STATES-PATENTS tlnited States Patent Delves-Broughton ELECTR OTIN NING WIRE mem .weo ni h wwd n m l S m k Le tv S m nm m Od u R m W Rmnu F a. on m w mw w mum m wot.. D d u S a m m h 6 h 1 mm m Bm.C now 6 tmn a P m .w.b SUSO S des .w hvwn W.US.1

PATENTEWR 3,869,371

SHEEI 1 2 F/GZ.

PATENTED HAR 41975 SHEET 2 BF 2 r. .ELECTROTINNING WIRE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of and apparatus for continuously electrotinning wire and in particular to an improved high speed, high current electrolytic process for tinning copper wire.

2. Description of the Prior Art One known method of continuously electrotinning a copper wire, described in British Pat. Nos. 743,404 and 743,405, employs stannous sulphate for the electrolyte. This methodv basically comprises passing a longitudinally moving .copper wire a plurality'of times through an electrolyte tank, each time passing the wire around an electrically conducting driven grooved drum which is' connected to the negative pole of a dc. current source, and a separate one of a plurality of insulating pulleys, the anodic current being supplied via anodes of tin immersed in the electrolyte. Typically the apparatus is such that the wire is horizontal when being plated and passes alternately through two plating tanks which are arranged one above the other between the pulleys and the drum. Using such an arrangement, electrolyte current densities of the order of 100 amps per square ft. are employed and the wire moves at a rate of 500 ft. per minute, the plating thickness being built up gradually during-passage through the electrolyte.

Electolytes, such as stannous fluoborate, which are capable of higher current densities of the order of, for example, 400 amps per sq; ft. are now available, with the result that with the same basic known method and apparatus, plating rates four times greater than obtainable with stannous sulphate can be achieved.

The use of stannous fluoborate for the electrolyte, however, results in a number of practical problems. The highly corrosive nature of the electrolyte means that plastics materials or rubber lined steel must be used for the tanks, pipework and pumps. In known arrangements using stannous sulphate, the tin anodes are positioned in the electrolyte tanks below the moving wire, but this produces problems, when using stannous fluoborate, in the method of contacting the anodes to the bus bars therefor, so that the latter are not corroded. In order to cope with the high current density (400 amps per sq. .ft.), the wire must be arranged'to pass in sufficient loops through the electrolyte'tanks so. -as to pass the current without causing overheating. In

addition, the higher running speeds which can be achieved with stannous fluoborate can cause hydrodynamic drag effects on the electrolyte in the tanks. With a large number of portions of wire passing through one tank in the same direction and at a high speed, quite a considerable wave of electrolyte can be caused to move .in this direction and spill over the end of the tank. This problem also occurs in connection with other processes, and the usual methods used. to counteract it involve systems of weirs or other baffles.

SUMMARY OF THEINVENTION drag effects are normally experienced. According to one aspect of the present invention there is provided apparatus for use in passing a longitudinally moving elongate article a plurality of times through a bath containing a liquid.

According to another aspect of the present invention thereis provided an apparatus for continuously depositing a metal coating on a longitudinally moving wire comprising passing the wire a plurality of times through a bath containing an electrolyte consisting of asolution ofa salt of the metal to be deposited, each time passing the wire in a loop around two rotatable conducting drums, at least one of which is connected to the negative pole ofa source of direct current, at least a portion of both sections of each wire loop between the drums being in a substantially common horizontal plane and passing through the electrolyte bath with the wire loop sections alternating so that adjacent sections move in.

opposite directions, the anodic current being supplied via one or more anodes of the metal to be deposited which extend into the electrolyte.

According to a furtheraspect of the present invention the bath is positioned between the drums, spacing and deflector means being positioned between the bath and the drums so as to cause the portions of the wire loop sections passing through the bath to be in a substantially common horizontal plane with alternate wire loop sections moving in opposite directions.

Embodiments of the present invention will now be described with reference to the accompanying drawings. I

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 schematically shows a side view of apparatus for use in electrotinning a wire according to one embodiment of the present invention, with the oppositely directed portions of. the wire shown having a vertical displacement for illustrative'purposes only,

FIG. 2 schematically shows a side view of apparatus for use in electrotinning a wire according to another embodiment similar to'that of FIG. I, and

FIG. 3 shows a partly'cutaway schematic view of the apparatus according to FIG. 2;

DESCRIPTION or THE PREFERRED EMBODIMENT As previously mentioned, one known method ofcontinuously electro -tinning wire consists of passing a wire in a series of loops around a conductive cathode contact grooved roller and a plurality of insulating roling the wire at high speed through the tanks will causespillover of the electrolyte from the tanks, which spill: overoccurs at opposite ends thereof.

The present invention is based on the recognition that if the two oppositely directed motions of the wire sections take place in approximately the same horizontal plane in a single tank or bath of electrolyte, with the sections of wire moving in one direction being alternatedwiththe sections moving in the oppositedirection, then the effects of drag in one direction will be at loops may be brought into substantially the same plane by lifting the lower sections 2 (FIG. 1) or lowering the upper sections 1 (FIG. 2). This can be readily achieved by use of insulating grooved spacing and deflector rollers, 3, which are ofa material that is unaffected by the electrolyte in the tank or bath 4, such as a plastics material. Both. sections of the wire loops therefore pass through the same electrolyte tank 4, and the way in whichthey pass into the tank and the way in which the tank is maintained with a certain level of'electrolyte, are similar to those used for conventional two tank plating'arrangements. These involve the'use of electrolyte reservoirs and pumps for replenishing the tank with electrolyte in place of that which has escaped via ports in the tank walls through which the wire enters and leaves the tank 4.

As can be seen from FIGS. 1 and 2, this arrangement of both sections of the wire loops within the same tank facilitates the arrangement of the anodes since they may be suspended from a bus bar arrangement above the tank so that they dip into the electrolyte. This arrangement ensures that the bus bar 8 and the anode supports (loops) 5 do not come into contact with the electrolyte and are, therefore, not-corroded thereby. Splash guards, as shown schematically'at 11 in FIG. 2, are used to prevent electrolyte coming into contact with the bus bar, etc.

The arrangement shown in FIG. 2 is shown in substantially greater detail in FIG. 3. Basically the apparatus comprises two rotatable cathode drums-6 and 7,

two multigrooved (grooves not shown for reasons of clarity) spacing and deflector rollers 3, a tank 4 for the electrolyte, typically stannous fluoborate, and a bus bar 8 connected to a source of positive potential and having arms 9 from which are suspended anodes 10 of pure tin by loops 5 of, for example, stainless steel, which a were connected thereto during the anode casting process. Not all of the anodes and arms have been shown for reasons of clarity. The drums 6 and 7 are electri cally conductive, i.e., bronze coated, at least on their outer surface, with which the wire 12 is in contact, and they are electrically connected to a common source of negative potential. The drum 7 is freely rotatable on a shaft 13, whilst the drum 6 is provided with a shaft 14 by means of which it can be driven by a motor (not shown). Both drums and shafts are provided with slip rings and brush, gear for making the cathode Contact. In the known plating arrangements mentioned before, the drum equivalent to drum 6 is provided with circumferential grooves for guiding and separation of theloops ofwire, but in the'apparatus of the present invention it is not necessary to provide grooves on the drums 6 and 7 since the grooved spacing and deflection rollers 3 perform the same functions and, being ofplastics material, are cheaper to provide with grooves, which may be molded therein, rather than the machining necessary of a metallic drum. The rollers 3 are rotatable about axles (not shown). The whole arrangement is provided within a housing 15 which is provided with shown) may be located above the tank 4 to facilitate loading and unloading of the electrodes.

ln a specific example of use of the apparatus in FIG. 3, an unplated copper wire 12 of, for example, 0.08 inches diameter is passed into the housing 15 via an entry port 16, after passing through a suitable degreasing process, fed under drum 6 and roller 3, through the tank 4, under roller 3, over and around drum 7, under roller 3, back through the tank 4, under roller 3, under and around the drum 6, thus forming one loop of wire, and back around the same course to form a total of 12 or 13 loops in all, each loop being separated from the others by location in separate ones of the grooves in rollers 3. The plated wire finally emerges from the apparatus in the direction of arrow 17. The exit direction is preferably vertical as shown, so that gravity assists in returning electrolyte to the apparatus from the plated wire, which-is subsequently thoroughly rinsed before being taken up on a driven takeup spool. In order to prevent the plating being damaged, plastics pulleys' should be used for guiding the plated wire from the plating apparatus to the takeup spool.

Typically the electrolyte comprises 26.8 ounces per gallon of-tin fluoborate, 10.8 ounces per gallon of tin (as metal), 6.7 ounces per gallon of free fluoboric acid,

0.8 ounces per gallon of bone glue and 0.13 ounces per gallon of beta naphthol; although the latter two :onstituents may be replaced by a suitable commercially available additive. The anodes are each of pure tin and may be made in a conventional manner.

In order to plate the copper wire with a radial thickness of, for example, approximately X 10 inches oftin at a speed of 2,000 ft. per minute (thus permitting a coating of 25 X 10' inches to be obtained on a 0.02 diameter wire after a 4 to 1 diameter reduction at a subsequent wire drawing process,) with the wire passing in 12 to 13'loops, the tank 4 must be approximately 10 feet long.

The electrolyte and cathode current density is of the' I order-of 400 amps per square ft.. at approximately the apparatus with a reasonable time between anode changes, e.g., 50 hours, the initial anode weight should be approximately 700-800 lbs., i.e., 40 anodes each weighing 20 lbs., since there must always be some residual tin left on the anodes; The remaining anode tin can be recast into new anodes in the conventional manner. The bronze coated drums 6 and 7 provide sufficient contact area with the'wire loops to reduce overheating of the wire which is required to transmit plating currents of 2,000 amps. which are considerably greater than the hitherto employed 500 amps.

The apparatus of the present invention therefore makes it possible to utilize high'current density electrolytes effectively, by providing adequate platingcurrent without overheating the wire and whilst overcoming fluid drag problemsassociated with high speed running.

Whilst the invention has been described with respect to the tinning ofcopper wire, it is alternativelypossible to use the same basic arrangement to deposit other metalon other sorts of wire. Various other modifications are possible, such'as only connecting one of the drums 6 and 7 to the negative voltage source, with 'a subsequent reduction in efficiency or speed in order to maintain efficiency. The basic apparatus of the invention may also be used in connection with other elongate members, for example insulated conductors, the bath being filled with, for example, water or degreasing fluids, in situations where hydrodynamic drag effects are likely to occur, Instead of one of the drums being driven in order to pull the elongate member through the apparatus, they may, alternatively, be both nondriven and pulling-through may be achieved purely by driven take-up-means arranged adjacent the exit of the apparatus. The spacing and deflector rollers may alternatively be composed of pluralities of separate pulleys arranged on common axles. The practicality of use with other elongate members or arrangements with nondriven drums will, in part, depend on the breaking load of the elongate member, since in thelatter case the breaking load must be sufficiently high for the member to pull itself through the system without breaking. The breaking load of the member imposes a limit on the number of turns possible with non-driven drums, so that it is preferable, in some cases, to drive one of the drums.

What is claimed is:

- tank and saiddrums to cause the: portions of saidwire 1. Apparatus for continuously depositing a metal coating on a longitudinally moving wire comprising a housing, a tank in said housing for a bath containing an electrolyte including a salt of the metal to be deposited,

means for passing said wire a plurality of times through said bath and end walls of said tank, said means including a pair of rotatable electrically conducting drums respectively positioned within said housing at opposite ends outside of said tank directing said wire into a plurality ofloops, direct current supply means, atleast one of said drums being connected to the negative terminal of said supply means, a pair of grooved rollers posiloops passing through said bath to be in a substantially common horizontal plane with alternate wires moving.

in opposite directions, and a plurality of anodes positioned along said tan-k in said bath and connected to the positive terminal of said supply means, said anodes being ofthe metal'to be deposited, said housing collecting electrolyte escaping from said tank and providing a source of electrolyte for said tank.

2. The apparatus of claim 1, wherein said rollers are.

formed of an insulating plastics material which is not corroded by the electrolyte.

3. The apparatus of claim 1, wherein said anodes include blocks of metal arranged in the bath substantially normally to the directions ofmovement of the wire loop sections. g

4. The apparatus of claim 1, wherein one of the drums is positively driven, and said grooved rollers are positioned on one side of said wire loops.

5. Apparatus for use in passing a longitudinally mov ing wire a plurality of times through a liquid bath com prising a housing, a tank in said housing for containing said bath, a pair of rotatable drums respectively positioned in said housing at opposite ends of said tank directing said wire into a plurality of wire loops passing through said bath and end walls of said tank, anda pair of grooved rollers positioned respectively between said opposite ends of said tank and said drums so as to cause said wire loops passing through said bath to be in a sub stantially common horizontal plane with alternate wires moving in opposite directions, said housing collecting electrolyte escaping from said tank and providing a source of electrolyte for said tank.

6. The apparatus of claim 5, wherein the exit direction of said wires from one of said drums is vertical to cause said bath to be returned by gravity to said housing.

d EINHED STATES PATENT OFFICE CERTEFEQATE 0F CURRECTEQN PATEM NO 3,869,371

DATEU 3 March 4, 1975 1 'NVENTORtS) James Delves-Broughton It is certified that EHOT appears In the above-identified patent and that said Letters Patent are hereby corrected as shown below:

G On the Title page, insert [32:] Priority July 27, 1972 [33] Great Britain Q 35089/ 72 gigncd and Sealed this ninth Day of September 1975 [SEAL] Attesl:

A RUTH C. MASON C. MARSHALL DANN Altesrl'ng Officer (mnmissinnvr uj'Parenls and Trademarks 

1. Apparatus for continuously depositing a metal coating on a longitudinally moving wire comprising a housing, a tank in said housing for a bath containing an electrolyte including a salt of the metal to be deposited, means for passing said wire a plurality of times through said bath and end walls of said tank, said means including a pair of rotatable electrically conducting drums respectively positioned within said housing at opposite ends outside of said tank directing said wire into a plurality of loops, direct current supply means, at least one of said drums being connected to the negative terminal of said supply means, a pair of grooved rollers positioned respectively between said opposite ends of said tank and said drums to cause the portions of said wire loops passing through said bath to be in a substantially common horizontal plane with alternate wires moving in opposite directions, and a plurality of anodes positioned along said tank in said bath and connected to the positive terminal of said supply means, said anodes being of the metal to be deposited, said housing collecting electrolyte escaping from said tank and providing a source of electrolyte for said tank.
 2. The apparatus of claim 1, wherein said rollers are formed of an insulating plastics material which is not corroded by the electrolyte.
 3. The apparatus of claim 1, wherein said anodes include blocks of metal arranged in the bath substantially normally to the directions of movement of the wire loop sections.
 4. The apparatus of claim 1, wherein one of the drums is positively driven, and said grooved rollers are positioned on one side of said wire loops.
 5. Apparatus for use in passing a longitudinally moving wire a plurality of times through a liquid bath comprising a housing, a tank in said housing for containing said bath, a pair of rotatable drums respectively positioned in said housing at opposite ends of said tank directing said wire into a plurality of wire loops passing through said bath and end walls of said tank, and a pair of grooved rollers positioned respectively between said opposite ends of said tank and said drums so as to cause said wire loops passing through said bath to be in a substantially common horizontal plane with alternate wires moving in opposite directions, said housing collecting electrolyte escaping from said tank and providing a source of electrolyte for said tank.
 6. The apparatus of claim 5, wherein the exit direction of said wires from one of said drums is vertical to cause said bath to be returned by gravity to said housing. 